In the manufacture of a semiconductor device such as a large scale integrated circuit (LSI) and a very large scale integrated circuit (VLSI), or a liquid crystal display panel, a semiconductor wafer or a mother substrate for a liquid crystal display panel is irradiated with exposure light via an exposure stencil such as a photomask or a reticle, whereby a pattern of the stencil is transferred onto the surface of the wafer or the mother substrate; however, if a dust particle exists on the stencil, this particle can absorb or bend the exposure light to thereby deform the pattern or blur the edges of the pattern transferred; furthermore the underlying surface is also blackened by soiling, whereby the size, quality, appearance and the like of the semiconductor wafer or the liquid crystal display panel mother substrate are degraded. In the present invention, an “exposure stencil” shall mean a mask for lithography or a reticle.
In order to prevent these problems, the operation of exposing the substrates is generally conducted in a clean room. However, even in a clean room environment, it is not always easy to keep the exposure stencil dust-free, and hence in order to fend off the dust from the surface of the exposure stencil, a pellicle which passes exposure light well is attached to cover the exposure stencil. In this manner, the dust is prevented from reaching the surface of the exposure stencil but can only alight on the pellicle membrane so that, if the exposure light is set to focus on the pattern of the exposure stencil, the dust on the pellicle membrane fails to shadow itself in the transferred pattern.
In general, a pellicle is manufactured by adhering a pellicle membrane to one annular face of a pellicle frame. The pellicle membrane is made of a nitrocellulose, cellulose acetate, a fluorine-containing polymer, or the like that has a high transmittance with respect to an exposure light (such as g-line, i-line, KrF excimer laser, ArF excimer laser, and F2 excimer laser). The pellicle frame is made of an aluminum alloy such as A7075, A6061, and A5052, which are black almite-anodized in the surface, or of a stainless steel or of polyethylene, etc.
In manufacturing a pellicle, the adhesion of the pellicle membrane to an annular face of the pellicle frame is effected by laying a solvent capable of dissolving the pellicle membrane on the annular face and placing the membrane over the solvent and drying the latter by air flow (ref. IP Publication 1), or by using an adhesive such as acrylic resin, epoxy resin and fluorine-containing resin (ref. IP Publication 2). Furthermore, on the other one of the two annular faces of the frame is laid a stencil-bonding agglutinant layer made of a polybutene resin, a polyvinyl acetate resin, an acrylic resin, a silicone resin or the like for attaching the pellicle frame to the exposure stencil, such as a reticle or a mask, and over this stencil-bonding agglutinant layer is laid a releasable liner for protecting the stencil-bonding agglutinant layer.
A pellicle is set in a manner such that the pellicle frame entirely surrounds the pattern region formed in the surface of the exposure stencil. As the pellicle is installed for the purpose of preventing the dust from adhering to the exposure stencil, the pattern region is thereby isolated from the external atmosphere so that the dust outside the pellicle cannot reach the pattern region.
In recent years, the design rules for LSI have been modified in the direction of heightening the resolution density as high as sub-quarter micron order, and this goes hand-in-hand with shortening of the exposure light wavelength. In other words, the formerly prevalent g-line (436 nm) and i-line (365 nm) created by mercury lamps are being replaced by KrF excimer laser (248 nm), ArF excimer laser (193 nm), F2 laser (157 nm) and the like. With the increasing exposure resolution accompanied by the shortening of the wavelengths of the exposure lights, a concern being harbored anew is the contamination with infinitesimal particles of such smaller sizes that conventionally caused scarce problem.
In order to hold a pellicle frame firmly while a pellicle is manufactured, transported or attached to or detached from an exposure stencil, a pellicle handling jig is used for the holding, and normally pins are provided to the jig to catch the pellicle frame. Hence the pellicle frame is usually formed with holes for receiving the jig pins. By inserting the jig pins into the jig receiving holes (hereinafter merely “jig holes”) in a manner such that the pins press themselves against the frame, the pellicle frame is grasped. The pressure of these pins is caused by the spring mechanism installed in each pin and thus the pins are capable of freely contracting in the lengthwise direction and regaining its original length.
Conventionally, when it was necessary to replace a pellicle handling jig to a different one between pellicle manufacturing steps, the pellicle frame held by the jig had to be released from the jig and temporarily placed on a table and then, after the replacement of the handling jigs in the manufacturing line, it was set to the different handling jig.
However, in this procedure, the pellicle frame, which was free of any contact with any other matter except at its jig holes, was obliged to get in contact with a foreign matter if not for a long time, and as the result the pellicle frame would get contaminated with a foreign particle or the like where it touched the foreign matter.